The present invention relates to an endodontic instrument for rapid mechanical widening of the canal mouth and rectification of the first two thirds of the dental root canals.
It can be used in endodontic operative practice during the phase which precedes preparation of the apical third, as described in the "three-stage" technique for the preparation of the corono-apical canal devised and developed by the same Applicant.
According to this technique, preparation of the canal is performed "progressively" starting from the occlusal surface towards the apex. Ideally it divides up the tooth into three zones and three phases or "stages" associated with said zones, the methodology and the corresponding instruments.
During the first "coronal phase", the "access cavity" is formed by means of a special diamond milling kit specifically devised by the Applicant. During the second phase, the middle third is prepared and the access cavity of the middle third is aligned (rectification), this being performed using a plurality of instruments of specific shape, flexibility, diameter and length, which form the subject of a previous patent granted to the Applicant in Italy under No. 1,211,650, in Switzerland under No. 678,008, in France under No. 2,617,704 and in the United States under U.S. Pat. No. 4,971,556. During the third phase, after completion of the preceding phases, the working length is measured at the apex and the apical third prepared.
When the second phase has been completed and prior to preparation of the apical third (third phase) of the aforementioned method, there is the need to widen further the canal mouth, eliminating completely and rapidly the remaining areas of "interference", namely those wall convexities or obstacles of a dentinal nature, which have prevented complete rectification of the first two thirds. This further widening is to be considered as particularly useful especially in the narrow and curved canals of the premolars and the upper and lower molars.
The instruments used previously during this stage include a rigid "rectifier" of the type described in Italian Patent No. 1,149,157, granted to the same Applicant. This "rectifier", indicated by 100 in FIG. 7, can be used, however, only in wide canals, such as for example those of the canines, where it works solely with the diamond-coated upper part, guided by the smooth nose 100a inserted into the middle third of the canal with an axial "in-out" and gradual lateral approach movement towards the cuspidal tip.
The most recent known instrumentation may also include titanium instruments which perform full mechanical rotation and, owing to their greater flexibility, are able to follow the curves and remain in the centre of the canals. Remaining in the centre of the canal, however, has the drawback that it widens indiscriminately "all" the wall thicknesses located around the instrument, with the risk of thinning and perforation of the thinner walls (ref. No. 50 in FIGS. 4 and 5).
The object of the present invention is therefore that of satisfying, without danger and in a locally more specific manner, the need of the endodontic procedure for widening and rectification of the first two thirds without any risk to the thinner walls in the region of the root bi- or trifurcations.